Does Lake Whatcom Qualify as an Impaired Waterbody?

Tom Pratum is a Lake Whatcom resident who is trying to help preserve the lake and put his PhD in chemistry to beneficial use.

Part I

Concern over the levels of toxins such as mercury, PCBs, dieldrin, and the like in Lake Whatcom has grown in recent years. Add to that the recent sewage overflow, and it is no surprise that a steady stream of letters to the editor on this subject have appeared in our local daily newspaper, The Bellingham Herald.

The subdivision moratorium recently enacted by the Whatcom County Council hopes to address some of these concerns by reducing non-point pollution sources due to anthropogenic (human origin) inputs. While the necessity of such measures is not in question for many of us, others ask – where is the science behind this?

One particularly controversial piece of the puzzle is the recent feud between the state Department of Ecology and Whatcom County Water District 10 over the listing of the lake under section 303(d) of the Clean Water Act as an impaired waterway for low levels of dissolved oxygen (see Whatcom Watch, August 2001, page 1 and October/November 2001, page 1), and the Total Maximum Daily Load (TMDL) study which has resulted from this listing. This is what I hope to address here.

When assessing a water body for its suitability as a water source, one characteristic that one would most likely want to see is a lack of overall biological activity. To view a water body exhibiting a high level of biological activity, merely leave your toilet un-cleaned and un-flushed for several weeks.

High biological activity generates masses of organisms – some of which may be pathogenic – which create a soupy (and possibly smelly) mess. Not only is such activity not conducive to use as a water source, it is certainly not conducive to use for swimming, fishing, or any other enjoyment.

Enter Lake Whatcom – certainly pristine and clear prior to the Caucasian settlement of this area. It was described in 1858 as “...a smooth sheet of water extending in an irregular semi-circle from southwest to southeast direction, fifteen or sixteen miles in length, with an average width of a mile, clear as crystal, sweet to the taste, cold, and in some places of fathomless depth.”1

Ignoring the slightly incorrect dimensions, would that be our description of the lake today? Some would think so. Some even argue that the lake is cleaner and clearer now than it was 50 years ago.

What proof is there of the “pristine nature”–or lack thereof – of this lake? Even more important, if its condition has eroded, what is the cause? To understand one aspect of this question we have to introduce a few concepts from limnology, the study of lakes.

Like all living creatures, lakes are born, they age, and eventually they die. This aging process is known as eutrophication, and normally takes many centuries. An aged eutrophic lake is characterized by high biological activity resulting in large amounts of biologically generated material, or biomass – much of which is dead and decaying on its bottom.

Such a lake would likely have a substantial amount of “muck” on the bottom and a variety of plants floating on the top. Not the first place one would stop for a drink of water or a swim.

The degree of eutrophication covers a continuous scale from young oligotrophic lakes to dying eutrophic lakes. Characterization along this scale is referred to as the trophic status of the lake. For the purposes of this discussion, we’ll use three commonly employed categories along this scale: oligotrophic–young, with low biological productivity, mesotrophic middle- aged, and eutrophic – dying, with high biological productivity.

Natural eutrophication occurs via a natural increase in the nutrient levels in a lake. External or allochthonous nutrients are carried naturally into the lake, providing the essential ingredients for increasing its internal or autochthonous biomass.

The two most important limiting nutrients in lakes are nitrogen and phosphorus – biological growth in the lake will be limited by the availability of these two elements.

As a natural process, this biomass is degraded (oxidatively degraded, or oxidized) by aerobic, or oxygen loving bacteria. Natural waters would be expected to contain some molecular oxygen (O2) since it dissolves in water from the air as well as being produced by photosynthetic (light harvesting) organisms (phytoplankton, most commonly algae) in the water itself, and can be mixed throughout the water column.

One might consider that the entities which are built up by photosynthesis during life — creating biomass — are oxidatively degraded upon death.

As any chemist will tell you, when one thing is oxidized, something else is reduced – this reduced material is also known as an electron acceptor. Dissolved oxygen in the water takes (accepts) electrons from the organic material to be oxidized, and is reduced to ultimately form carbon dioxide (CO2) and water (H2O).2

When sufficient decaying organic matter exists to remove the dissolved oxygen from the water, decay does not cease. Instead, the organisms responsible for the decay or oxidation of the organic matter switch to degradation pathways which can utilize other electron acceptors.

Instead of using oxygen, they may utilize sulfur (as sulfate–SO4). Instead of making water, they make hydrogen sulfide (H2S), a toxic gas which gives the familiar smell of rotten eggs (but also dissolves in water).

To summarize: increased nutrients lead to greater biological productivity which leads to an increase in decaying biomass which leads to a decrease in dissolved oxygen. Aquatic species which rely on oxygen for respiration (e.g. fish of all types) are likely to be imperiled by the resulting anoxic conditions. Among other chemical changes that may be observed due to eutrophic conditions are the increased level of hydrogen sulfide noted above, and an increase in soluble iron levels.3

So the question then becomes, to what extent do the activities of humans contribute to accelerating the entry of allochthonous nutrients into the lake, and thus leading to its speedy demise. Lawn fertilizers, septic tanks, pet waste, land disturbance, and a myriad of other man-made activities may contribute to the nutrient loading of the lake.

This is of great concern, and is the subject of both state and federal regulations. In particular, section 303 of the federal Clean Water Act of 1972 dictates that state administrators adopt standards which are “in accordance with the applicable requirements of the Act.” As the stated intent of the Clean Water Act is “Restoration and maintenance of chemical, physical and biological integrity of Nation’s waters...,” reversal or prevention of eutrophication is a high priority.

To assess the state of eutrophication, one can either look at the causes – those allochthonous nutrient sources – or, the effects – the increase in biomass and/or decrease in oxygen. Since the lake’s productivity is likely to be nitrogen and phosphorous limited, one indication of a lake’s trophic status would be its nitrogen and phosphorous levels.

Biological activity makes the water turbid (from the growth of organisms), so another measure would be to see how far an object can be seen in the water.4 To get an indication of the photosynthetic productivity of the lake, a measurement of the chlorophyll-a absorbance of the water can be taken.5

Dissolved oxygen levels can also be measured as an indication of how much oxidation of organic matter is occurring, and thus of the level of decaying biomass in the lake. In a monomictic lake such as Lake Whatcom, the lake becomes thermally stratified during the summer, and “turns over” or mixes during the late fall.6

During the stratified period, the lower, cooler layer (hypolimnion) is of greatest interest as far as dissolved oxygen content is concerned. This layer is isolated from the surface where additional oxygen could enter by diffusion from the air, and is in contact with the bottom where decay is occurring.

The state of Washington has set surface water quality standards, in keeping with the federal Clean Water Act (Federal Regulation 40 CFR 131), which are promulgated in chapter 173-201A of the Washington Administrative Code (WAC). Particular indicators given there are the total phosphorous (TP) concentration of the lake, and its dissolved oxygen (DO) content.

While the assessment of TP is based on an already determined trophic status, that for DO is given simply as “…no measurable decrease from natural conditions.” Natural conditions are defined as those that existed “…before any human-caused pollution.” This would be presumably be before that description of the crystal clear, sweet tasting lake given in 1858.

Unfortunately, a dearth of data exists on the historical level of anything in Lake Whatcom. Fortunately, Professor Robin Matthews and her group at Western Washington University have acquired substantial data on the lake over approximately the past 15 years.

There is an indication of low oxygen levels extending back at least 30 years from other data, but are these levels getting worse, or better? The trend is ever important, and it is assessment of that trend from data provided by Professor Matthews which has led to the listing of the lake on the state’s 303(d) list for low DO, and the controversy surrounding it.

Next Month — Part II
The data—for and against 303(d) listing and the TMDL study.